NEW YORK (Reuters health) - Among premenopausal women treated for hormone-responsive breast cancer with adjuvant anastrozole, body mass index (BMI) has a significant impact on outcomes, an Austrian study shows.

The use of aromatase inhibitors in premenopausal women, combined with ovarian suppression, is “attractive in principle,” the researcher note in their report in the Journal of Clinical Oncology online May 9. While early trial results indicate that the strategy is effective, it’s not known if women with high aromatase levels derive the same benefit as those with low levels.

“We hypothesized that BMI as a surrogate parameter for total body aromatization impacts on the efficacy of aromatase inhibitors,” explain Dr. Michael Gnant, at the Medical University of Vienna, and colleagues. They examined this question using data from the ABCSG-12 trial, which compared goserelin in combination with tamoxifen versus anastrozole in premenopausal patients with endocrine-responsive breast cancer.

Overall, there was a trend for worse disease-free survival in the 573 overweight women in the study compared with the 1111 normal-weight patients, with a disease-recurrence hazard ratio 1.24 (p=0.15). The trend for overall survival was similar, with a mortality HR of 1.49 (p=0.10), according to the report.

On further analysis, it was apparent that this trend was driven by the anastrozole group, since BMI was not a factor in women treated with tamoxifen.

When treated with anastrozole, the risk of disease recurrence in overweight patients was 15.1% compared with 9.0% in normal weight women (p=0.02). This translates to a hazard ratio of 1.60, the authors found.

Furthermore, in the anastrozole arm, overweight patients had more than double the risk of death compared with normal weight patients who (HR 2.14, p=0.01).

“Clearly, these results should currently be viewed as hypothesis generating because of the retrospective nature of our analyses,” Dr. Gnant and colleagues advise. “In current clinical practice, however, physicians may want to include this aspect in the risk-benefit assessment in counseling overweight premenopausal patients with breast cancer about their choice of adjuvant endocrine treatment.”

Impact of Body Mass Index on the Efficacy of Endocrine Therapy in Premenopausal Patients With Breast Cancer: An Analysis of the Prospective ABCSG-12 Trial
J Clin Oncol 2011;29.